Freezemeter



Sept. 8, 1953 `1.w.D|cKEY E'TAL 2,6515194 FREEZEMETER Filed Jan. 21, 1952 2 sheets-sheet 1 uw l v' @i (fyi 4% 3P* INVEyToRs z @www ORNEY WITNESS."

Sept. 8, 1953 J. w. DICKEY ET AL 651)1'94 FREEZEMEJIER Filed Jan. 21, 1952 2 sheets-sheet 2 l da AT HNEY Patented Sept. 8, 1 953 FREEZEMETER John W. Dickey, Newfield, and E. Elliott Hood, Elmira, N. Y., assignors to Bendix Aviation Corporation, a corporation of Delaware Application January 21, 1952, Serial No. 267,452

4 claims. (c1. 'z3-17) The present invention relates to a freezemeter and more particularly to a device for determining the thawing point-of a liquid.

rllhe present disclosure is in the nature of an improvement of the structure shown in the application of Dickey, Serial No. 83,986, led MarchV 28, 1949, and assigned to the lassignee of the present application.

The Dickey application discloses an instrument for freezing a small sample of liquid to be tested, then allowing it to thaw and recording the temperatur at which it begins to ow under a constant pressure. Experience with the instrument disclosed in said Dickey application has proved that with water mixtures of the kso-called f'permanent antifreeze type having an ethylene glycol base, the freezing point and the thawing point are either indistinguishable or bear a constant relation to each other such that either one makes a satisfactory basis for classifying liquid coolants.

It is an object of the present invention to provide a novel freezemeter of the above type incorporating novel structure for withdrawing heat from the sample to be frozen.

It is another object to provide such a device in which the heat exchanger is arranged to use the cooling effect produced by the release of liquifled carbon dioxide.

It is another object to provide such a device in which the expansion of the released carbon dioxide is controlled in a progresive manner from the point where it enters the heat exchanger so as to reduce the tendency to clog the heat exchanger with localized deposits of snow.

It is another object to providesuch a device in which the cooling eiTect of the expanded carbon dioxide gas is spread out substantially uniformly over the body of the heat exchanger containing the sample to be frozen.

Further objects and advantages will be apparent from the following description taken in connection with the accompanying drawing in which:

' Fig. 1 is a vertical substantially mid-sectional View of a preferred embodiment of the invention showing the parts in normal or idle position.

Fig. 2 -is an enlarged sectional detail of the heat exchanger.

Fig. 3v is a section taken substantiallyon the line 3-3 of Fig. 2.

Fig. 4'is a view similar to Fig. l showing a modified form of heat exchanger.

Fig. 5 is an enlarged sectional detail of the heat exchanger shown in Fig. 4, and Y Fig. 6 is an end view of the heat exchanger asshowninFigS. .I

In Fig. 1 of the drawing there is illustrated a metallic frame or housing I in which is mounted a mechanical type of thermometer generallyindicated by the numeral 2. The thermometer comprises a stem 3 in which a staif 4 is rotatably 3 of the thermometer through a spiral ribbon of bimetal 8 which forms the heat-sensitive element of the thermometer. n

The stem 3 of the thermometer is surroundedv The other end of the tube 9 is mounted in a sleeve 20 of insulating material such as nylon, which sleeve is seated in a ring 20 of hard rubber or the like xedly mounted in a frame member I9 having a passage 2I leading to a chamber 22 which isclosed by a flexible diaphragm 23. A spring 24 in a pump chamber 25 normally flexes the diaphragm 23.in the direction to eject the contents of chamber 22, by means of a piston member 26 actingon the diaphragm. Means for compressing the spring 24 to retract vthe diaphragm is provided in the form of a manually rotatable cup member 2l having an inclined pin -and slot connection 28 with the pump chamber 25, and connected as shown at 29 with a plunger 3l fixed to the piston 26.

A cylindrical support 32 is flxedly mounted on the frame I and is arranged to receive the lower f end ,of a storage cylinder or ask 33 containing liquiied carbon dioxide under pressure. mechanism for the carbon dioxide cylinder, indicated generally by the numeral 34, is releasably connected tothe cylindrical support 32 as shown at35, so that rotation of the carbon dioxide flask by the operator controls the admission of gas from the ask through a small fixed aperture 3i) into a nipple 36 forming part of a heat exchanger unit 3'I.V

. The heat exchanger, as best shown in Fig. 2, comprises a portion of the tube 9 which is provided with a plurality of radial iins 38, and a funnel shaped ductmember 39 which is attached to the gas discharge niplole 36 andconducts the mixture of gas and snow escaping vfrom the aperture 30 over the ns 38 and around the tube 9. The funnel member 39 terminates in a sleeve 4l of metallic screening material which surrounds the tube 9 and fins 38 and is open at its ends as shown in Fig. 2. Sleeve 4l is slotted on its upper side for connection with the mouth of the funnelshaped duct 39 as best shown at 4l)` in Fig- 3, the arrangement beingsuch that the freezing gas and snow mixture is distributed substantially uniformly along the finned portion of the tube 9 and brought into intimate contact with the. surfaces of the tube and fins, without building up any substantial back pressure.

The heat exchanger is so dimensioned that theheat-sensitive element 8 of the thermometer lies wholly Within the heat exchanger so as to, be uniformly cooled thereby during the freezing process.

Means are provided for automatically arresting the thermometer needle at the thawing peint. of the sample. As here shown this. means. come. prises a magnet 42. which. is slidably mounted in. a cylindrical passage 4.3 in the frame member l2., in Contact with a. flexible diaphragm 40. in such a position that fluid pressure in the passage i3 causes the magnet to be moved into contact. with the thermometer casing 6. whereby it. becomes effective to operate` an arresting device indicated generally by numeral. M.. Since the arresting structure is not part of the.. present invention, further description thereof believed unneces-y sary.

In the operation of the devceto determine the thawing point. of an unknown liquid such asthe coolant for an inter-nal combustion. engine, the. inlet fitting l1 is. introduced into the engine radiator, the valve l5, is openedand the1 rotatable pump member 2l is. rotated to retract the diaphragm 23 and thereby draw a sample of the liquid up. through the tube. 9.. into the chamber 22. The valve l5 is then closed, and the carbon dioxide flask 33 rotatedto, open the. valve 3d and admit refrigerating gas. through the aperture 3.0 into the heat exchanger 31.. The. intense coldY so produced around the finned tube. quikiy extracts the heat from the portion of the, liquid surrounding the thermometer stem 3 within the. tube. 9 causing it to. congeal, After the sample is frozen, the flask valve 34. is. closed, and the pump member 21. is released so. as. to, allow` 'the spring 24 to press against the. diaphragm 2;3., and thus apply. pressure tending to eject. the.. liquidA from the. chamber 22.

The frozen sample is then allowed to thaw by conduction ofheat from the surrounding atmosphere and connected parts and when this.- occurs, the pressure in pump chamber 22A is. transmitted to the passage i3. Since this passage is. closed by the valve l5, the pressure. therein is effectiveV to move the magnet 42;, causing.` the thermometer needle to be arrested at thethawing point of the. sample.

It has been found in the operation ofA this. device that it sometimes happens that the freez.- ing operation is continued until the liquid in the.. outer ends of tube 9, andin the sleeve. 2.0. is frozen, and that when this occurs, theA sample which thermometer stem may, thaw first, so that the reading of the instrument becomes; unreliable. In order to conduct a small amount of heat from the frame ofthe instrument through the sleeve 20, a copper wirea is arranged to traverse the sleeve, its outer end being flattened and pressed into the passage 2t in frame member le se as te make firm Contact therewith. At the.

opposite end of the tube 9, heat is received directly from the frame member l2 through the joint at Il. This arrangement insures that when the frozen material is allowed to thaw, the material surrounding the heat-sensitive element of the thermometer will be the last to thaw and the thermometer willA therefore indieate accurately the thawing temperature of the sample at the instant the needle is arrested by the hydraulic pressure transmitted through the thawed sample.

In the embodiment of the invention illustrated at Figures 4 to 6, the elements of the thermometer, sampling system, and source of freezing gas are the same as in the rst embodiment described and theparts are similarly numbered. embodiment however has a modified form of heat exchanger. As here shown, a small thin- Walled tube 50 is wound around the thermometer stem 3 in the form of a spiral having spaced convolutions and is connected at one end by a conduit 5| to a. nipple 5.2i communicating with the passage I3 in the trame member l2. At; its other end, tube 50 is connected. bv a Conduit 53 to a nipple 5.4 communicating; with the. chamber 2v2.in the frame. member lllAIV A funnel-shaped member 5.5 iS, attached te the gas discharge nipple 3B and termiria.jti esin a split. sleeve 5.6 which surrounds the. spiral tube 5u. and the thermometer stem 3. se as to. cause the freer.- ing gas to traverse the space between the con volutions of the spiral tube 5D, allowing the gas to emerge at the ends 0i. the sleeve 5B.

In orderto ensure that any liquid frozen4 in the tubing outside. the, bedr ofzthe heat. exchanger thaws. before that which surrounds the ther-A mometer stem inside the. heet; exchanger.. it has been found desirable. to mount.. e, metall-1Q bed-y- Qi substantial mass and heat capacity in thermal contact with said tubing. For this.. purpose a bar- 51 of suitable material such as brass is eon.A neeted to the. projecting ends of the tube. 50, and serves to supplya small amount of'A heat tQ eccelerate the thawing 0f any frozen material between the bar and the heat` exchanger. This arrangement ensures that when the sample surroundingthe heatfsensitive element of the ther-V mometer melts, thereis no obstruction which might prevent the immediate arrest ofA thether-y mometer needle.

The operation of this embodiment ofthe'. invention is the same asA the fil-fst. embodiment, and further description thereof is believed. te be. uri-.- necessary.

Although but two; embodiments of the. inyen. tion have been shown and. described in detail, it will be understood that other embodiments are. possible and that changes; may lhe made in the form and arrangement or the parts without de.- parting from the spirit of the, invention,

We claim:

i. In an apparatus for.- determining the thawing point of a liquid, aA thermometer having a tubular stem with a temperature-responsive element therein, a freezingy tube surrounding the stem and extending beyond.; the temperatura. responsive element. therein, means for lling the tube with the liquid to be tested, a. sQullQe Qf at low temperature terminating in al nipple spaced laterally from said tube at an intermediate point.

in its length, an openeended; slotted sleeve partially surrounding the tube, and. a tapered; con: duit connected. at its throatto the nipple and at its mouth to the slot of the sleeve.

2; Anapparatus as set. forth. inclaim L in C which the sleeve located around thefreeeing tube is formed of reticulated material which permits the escape of the freezing gas after it has passed JOHN W. DICKEY. E. ELLIOTT HOOD.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 1,443,537 Hortvet Jan. 30, 1923 1,632,748 Parsons June 14, 1927 1,680,636 Rowan Aug. 14, 1928 2,079,344 Geyer May 4, 1937 2,591,084 Martin Apr. 1, 1952 

